A process for imagewise forming a polymer image using an organic compound as a photopolymerization initiator has been well known. But, the photopolymerization initiator requires a strong light exposure or an exposure in a long term, since the sensitivity of the photopolymerization initiator is much lower than the sensitivity of silver halide. The limited sensitivity of the photopolymerization initiator restricts the use of the image recording process.
On the other hand, a process for initiating a polymerization reaction using silver halide as a light sensor has also been well known. For example, a process wherein a polymerization reaction is initiated by a radical which is formed from an oxidation product of a reducing agent in the development step of silver halide is described in Japanese Patent Publications No. 45(1970)-11149, No. 45(1970)-30338, No. 46(1971)-6581, No. 46(1971)-21723 (the contents of these three Publications are described in U.S. Pat. No. 3,697,275 and German Patent No. 1,720,665), No. 47(1972)-12638 (corresponding to U.S. Pat. No. 3,707,379 and German Patent No. 1,924,721), No. 47(1972)-14667 (corresponding to U.S. Pat. No. 3,767,400 and German Patent No. 1,797,193), No. 47(1972)-14668 (corresponding to U.S. Pat. No. 3,782,943 and German Patent No. 2,000,110), No. 47(1972)-14669 (corresponding to U.S. Pat. No. 3,697,263 and German Patent No. 1,919,841), No. 47(1972)-16357, No. 47(1972)-18585 (corresponding to U.S. Pat. No. 3,756,818 and German Patent No. 1,772,146), No. 47(1972)-20741 (corresponding to U.S. Pat. No. 3,687,667 and German Patent No. 1,936,260), No. 49(1974)-1569 (corresponding to U.S. Pat. No. 3,874,947 and German Patent No. 1,942,168), No. 49(1974)-1570 (corresponding to U.S. Pat. No. 3,756,820 and German Patent No. 1,954,768) and No. 49(1974)-10697 (corresponding to U.S. Pat. No. 3,746,542 and German Patent No. 1,961,920), and Japanese Patent Provisional Publications No. 57(1982)-138632, No. 57(1982)-142638, No. 57(1982)-176033, No. 58(1983)-107529 (corresponding to U.S. Pat. No. 4,560,637), No. 58(1983)-169143 and No. 58(1983)-174947.
Further, Japanese Patent Publication No. 41(1966)-18862 (corresponding to U.S. Pat. No. 3,241,962) discloses a process wherein a polymerization reaction is initiated by a radical which is formed from a peroxide by a redox reaction of the peroxide with developed silver; Japanese Patent Publication No. 39(1964)-2657 (corresponding to U.S. Pat. No. 3,345,164) discloses a process wherein a polymerization reaction is initiated by a radical which is formed from a peroxide by a redox reaction of the peroxide with silver ion which remains within the unexposed area; U.S. Pat. No. 3,029,145 discloses a process wherein a polymerization reaction is initiated by a radical which is formed from a peroxide by a redox reaction of the peroxide with an iron (I) salt which remains within the unexposed area after development of silver halide with the iron (I) salt; and Japanese Patent Provisional Publication No. 55(1980)-149939 (corresponding to U.S. Pat. No. 4,287,290) discloses a process wherein a polymerization reaction is directly initiated by a reducing agent which remains within the unexposed area after development of silver halide. The above-mentioned image recording processes have a high sensitivity to form a polymer image. In theory the sensitivity of the processes corresponds to the sensitivity of silver halide. However, the processes need a wet development using a developing solution. The wet development is an obstacle to design for an image recording apparatus.
As is mentioned above, the problem of the process using a photopolymerization initiator is the low sensitivity, and the problem of the process using silver halide as a light sensor is the wet development. In order to solve both of the problems, another image recording process is proposed in Japanese Patent Provisional Publication No. 61(1986)-75342 (corresponding to U.S. Pat. No. 4,649,098). The process comprises the three steps of: (I) imagewise exposing silver halide to light to form a latent image of the silver halide; (II) developing the formed latent image of the silver halide with a reducing agent; and (III) conducting substantially uniform light exposure in the presence of a photopolymerization initiator and a polymerizable vinyl monomer (ethylenically unsaturated polymerizable compound) to form a polymer image.
The reducing agent used in the process disclosed in Japanese Patent Provisional Publication No. 61(1986)-75342 has (1) a function as a developing agent for silver halide; (2) a function as a polymerization inhibitor for the polymerizable vinyl monomer; and (3) a property of losing the function as a polymerization inhibitor after development of silver halide. Thus a polymer image is formed within the area where the reducing agent is not present (i.e., the area where the oxidation product of the reducing agent has been formed).
An embodiment of the image recording process disclosed in Japanese Patent Provisional Publication No. 61(1986)-75342 is hereinafter described in detail referring to FIGS. 6 to 9.
FIG. 6 is a sectional view schematically illustrating an embodiment of the image recording material disclosed in Japanese Patent Provisional Publication No. 61(1986)-75342.
As is shown in FIG. 6, the image recording material comprises a support (61) and an image recording layer (62). The image recording layer contains silver halide (.quadrature.), a reducing agent (.gradient.) having a function as a polymerization inhibitor, a photopolymerization initiator (.largecircle.) and a polymerizable vinyl monomer (ethylenically unsaturated polymerizable compound).
FIG. 7 is a sectional view schematically illustrating the step of imagewise exposing to light the image recording material.
FIG. 7-a is a diagram showing the reaction at the step of imagewise exposing to light the image recording material.
As is shown in FIG. 7 and FIG. 7-a, the latent image of silver halide ( ) is formed within the exposed area (71). The silver halide (.quadrature.) remains within the unexposed area (72).
FIG. 8 is a sectional view schematically illustrating the step of heating the image recording material.
FIG. 8-a is a diagram showing the reaction at the step of heating the image recording material.
As is shown in FIG. 8 and FIG. 8-a, the silver halide is developed ( ), and an oxidation product of the reducing agent ( ) is formed within the area (81) where the latent image of silver halide ( ) has been formed. The reducing agent (.gradient.) having a function as a polymerization inhibitor remains within the area (82) where the latent image of silver halide has not been formed.
FIG. 9 is a sectional view schematically illustrating the step of uniformly exposing to light the image recording material.
As is shown in FIG. 9, the polymerizable compound is polymerized with the photopolymerization initiator (.largecircle.) within the area (91) where the oxidation product of the reducing agent ( ), which loses the function as a polymerization inhibitor, has been formed. On the other hand, the polymerizable compound is not polymerized within the area (92) where the reducing agent (.gradient.) having a function as a polymerization inhibitor remains.
As is described above, a polymer image is formed within the area exposed to light at the imagewise exposure according to the image recording process disclosed in Japanese Patent Provisional Publication No. 61(1986)-75342.